This invention relates to a method for measuring surface roughness according to a tracer method, and more particularly it relates to a method for measuring surface roughness of an object indirectly by making two different kinds of replicas successively and measuring surface roughness of the second replica.
The term "surface roughness" means unevenness or ruggedness present of the surface of an object at narrow spacing, and the configuration or the condition of distribution of such surface roughness varies widely depending on the working process or surface treatment method used on the object.
There are known generally two different types of methods for measuring surface roughness: a direct tracer method in which surface roughness of the object is measured directly with a tracer, and an optical method in which light rays are applied to the object surface and its roughness is measured optically by way of reflection or interference of the light rays applied.
According to the optical method, it needs to make replicas of the object to be measured and also, in many cases, evaporation of metal on the replica surface is required for enhancing reflexibility of the replica surface. On the other hand, the tracer method involves the problem that scratches or flaws might be given to the object surface by the tracer, and this method is also subject to dimensional restriction by the tracing apparatus employed, so that this method may prove useless in certain specific applications, for example measurement of the internal wall surface of a fine tube. Further, the optical method is intended for measurement of a minute portion by use of a microscope, so that although this method is suited for measurement of a limited area, it is hardly possible with this method to correctly know the general trend or distribution of roughness on a large-sized object.